A system for classifying a user touch event by a user interacting with a device as an intended key is provided. For different hand postures (e.g., holding device with right hand and entering text with right thumb), the system provides a touch pattern model indicating how the user interacts using that hand posture. The system receives an indication of a user touch event and identifies the hand posture of the user. The system then determines the intended key based on the user touch event and a touch pattern model for the identified hand posture. A system is also provided for determining the amount a presser a user is applying to the device based on dampening of vibrations as measured by an inertial sensor. A system is provided that uses motion of the device as measured by an inertial sensor to improve the accuracy of text entry.